The present invention relates to a ventilation fan system of the type in which a duct frame is fitted into a ventilation hole formed through a wall of a building from the outside thereof, a ventilation fan as well as a shutter (which is located at the leeward of the fan in case of the fan being used as an exhaust fan) are installed within the duct frame, and an exhaust fan frame with a switch adapted to be opened or closed depending upon whether the shutter is closed or opened is inserted into the duct frame.
According to the present invention, a box-shaped duct frame with an outside louver or grill attached to the outside opening of the duct frame is fitted into a ventilation hole, and a ventilation fan frame with a ventilation fan and a shutter installed therein is fitted into the duct frame from the inside of the building, the shutter being operatively interlocked with the ventilation fan and being located at the leeward side of the fan when the latter is used as an exhaust fan. Since the ventilation fan frame is so designed as to be slidably fitted into the-duct frame, the ventilation system may be readily installed regardless of the thickness of the wall or even when the wall is of a double-wall type with an air layer in such a way that the flowing of the exhausted or forced air and rain water into the air layer may be completely eliminated. Since a switch adapted to open or close depending upon whether the shutter is closed or opened is also attached to the ventilation fan frame, the relative distance between the switch and the shutter is constant regardless of the thickness of the wall so that the adjustment of the length of the pull-string of the switch may be eliminated. Since the shutter is located at the midpoint of the ventilation hole, the flapping of the shutter blades caused by the wind may be minimized as compared with the system with the shutter attached to the outside opening of the ventilation hole. When the ventilation fan is used as an exhaust fan, the shutter is located at the leeward side thereof so that the entrance of rain water into the motor of the ventilation fan may be prevented. According to the present invention, the duct frame consists of four side plates of the same dimensions and configuration assembled in the form of a box with the opened top and bottom at a job site. Therefore, the dimensions of the package of the ventilation fan system may be reduced, whereby the packing and crating, storage and transportation costs may be reduced.
In one conventional ventilation system, a duct frame with a shutter attached to the outside opening thereof is fitted from the outside of a building into a ventilation hole formed through a wall, and then a ventilation fan frame with a ventilation fan installed therein is also fitted from the outside into the duct frame. When the system is so designed that the shutter is automatically opened by the draft produced by the fan, device operated from the inside of the building for opening the shutter is not provided. But in case of the system of the type in which the fan is driven only after the shutter is wide opened, the shutter is loaded with a bias spring so that the shutter is normally opened. And the shutter is connected to a pull-string inside the building in such a way when the string is pulled-down to close the shutter and is held in pulled-down position, the string opens a switch installed inside the building and connected to the electrical circuit of the fan, whereby the fan is stopped. The distance between the shutter outside of the building and the switch inside the building cahanges depending upon the thickness of the wall so that the length of the pull-string must be adjusted from one job site to another.
In another prior art ventilation system, the ventilation fan is so arranged as to be driven when the shutter installed inside the building is opened. The distance between the shutter and the switch is, therefore, constant regardless of the wall thickness. However, when the fan is used as an exhaust fan, the rain water tends to enter into the motor of the fan because the shutter is located inwardly of the fan, thus resulting in damage to the fan motor.
In both systems described above, the length of the duct frame is made longer so that it may be installed even when the wall thickness is greater. As a result, the dimensions of the package are increased, resulting in the increase in the packing and crating, storage and transportation costs.
In a cold district, the wall of a building is, in general, of the double-wall type with an air insulating layer formed between the outer and inner walls. When the length of the duct frame is made shorter in order to reduce the dimensions of the package and when such duct frame is installed in the ventilation hole, the exhaust or forced air and rain water flow into the air layer, damaging the wall construction.